Hi Stella.
The camera is a Nikon D70s, lense 18 - 70mm
pics were taken in A mode (Aperture priority)
ISO 200, shutter speed 1/60 F22, I had my SB800
on board the camera to get as much light on the fish as I could.
Just angle your camera slightly so the flash dosn't reflect
back at you and try and lock the fish in focus by pressing
the shutter button halfway before taking the pic.
The distance from the fish varies according to where they
are swimming in the tank but unless you have a macro/zoom lense
try and get as close as you can without scaring the fish.
Hope this helps, Mike.